Born February 26, 1957, in New York City, New York, Mullen grew up in the Hell's Kitchen neighborhood of Manhattan when it was controlled by the Gambino crime family.[1] It was a rough neighborhood; Mullen later said that many of the people he grew up with fell into gangs and drug use, and several died before turning 21.[2] He has three brothers, Ken, Tom Jr. and Brian, and a sister, Debbie.[3]

The Mullen family lived less than a block from Madison Square Garden, where Joe's father Tom was a longtime employee on the ice and maintenance staffs. Joe and his brothers often hung around the arena with their father, taking old sticks to play with.[3] He began playing roller hockey at the age of five, playing in a concrete schoolyard and using a sanded down roll of electrical tape as a puck.[2] The boys' schoolyard games served as a partial inspiration for New York Rangers' general manager, Emile Francis, to create the Metropolitan Junior Hockey Association in 1966.[1] Mullen did not learn to ice skate until he was ten years old, but at the age of 14 joined the Metropolitan association as one of the league's youngest players.[3] Mullen played four seasons in the league between 1971 and 1975.[4] He scored 71 goals in 1973–74, then 182 points in 40 games the following season. Mullen's 110 goals in 1974–75 was 52 more than his nearest competitor.[3]

Boston College offered Mullen a partial scholarship for the 1975–76 season to attend and play for the Eagles hockey program. He paid $700 out of his own pocket in the first year, but after scoring 34 points in 24 games as a freshman, the school gave him a full scholarship.[5] Including tournament games, he led the Eagles in goals the following three seasons with 39, 38 and 30 respectively, and points in 1977–78 with 68 and in 1978–79 with 56.[6] Mullen led the Eagles to the Eastern College Athletic Conference (ECAC) championship in 1977–78, and was named an all-star of the 1978 National Collegiate Athletic Association (NCAA) tournament.[7] He scored a goal in the championship game, but the Eagles lost to cross-town rival Boston University, 5–3.[8]

In four seasons with Boston College, Mullen set school records of 110 goals and 212 points (both subsequently broken).[9] He was named to the All-ECAC, All-New England and NCAA All-American teams in 1978 and 1979.[5][10] He won the Walter Brown Award in 1978 as the top American-born player in New England,[8] and was the team captain in 1978–79.[11] Boston College has twice honored Mullen; He was inducted into the school's Varsity Club Hall of Fame in 1998, while the hockey program retired his jersey number 21 the following year.[12]

Mullen returned to Salt Lake for the 1980–81 season where he scored 59 goals and led the league with 117 points.[15] He was named to the first all-star team and won the CHL's Most Valuable Player Award.[14] Opening the 1981–82 season with Salt Lake, Mullen had 21 goals in 27 games before he was recalled to St. Louis.[4] He scored his first two NHL goals on January 5, 1981, against the Minnesota North Stars. They came eight seconds apart and set a Blues' franchise record for fastest two goals by one player.[3] Mullen scored 25 goals for the Blues that season and became the first player in history to score at least 20 goals in both the minor leagues and the NHL in the same season.[1]

The Flames felt they needed a quality offensive player and expected Mullen to fulfill that role.[19] As it was the first time in his career he had been traded, Mullen was initially upset at the move. He was awed by the reaction he received from fans in Calgary however; fans greeted him warmly even as his flight landed to arrive in the city. Mullen described the experience as being "almost like ... an instant celebrity".[5] He quickly established himself as a fan favorite, scoring 38 points in 29 games to end the regular season.[20] He then led the league with 12 goals in the 1986 Stanley Cup Playoffs.[14] The Flames reached the final for the first time in franchise history, but lost to the Montreal Canadiens in five games.[16] Mullen set a personal best of 47 goals in his first full year in Calgary, 1986–87, and with only 14 penalty minutes on the season, was voted the winner of the Lady Byng Memorial Trophy as the NHL's most gentlemanly player.[15]

Though he played in his second All-Star Game in 1990,[22] Mullen's production fell by 41 points, to 69, and he failed to score at least 40 goals for the first time in six seasons.[4] Concerned about his age, the Flames chose to trade the 33-year-old Mullen following the season.[24] He was sent to the Pittsburgh Penguins in a draft day trade on June 16, 1990, in exchange for Pittsburgh's second round selection.[25]

The move to Pittsburgh brought Mullen closer to his New York home and fulfilled his desire to raise his family in his native United States. He also appreciated that the Penguins felt he could aid their team. Penguins' coach Bob Johnson, who had previously coached him in Calgary, influenced the team's decision to acquire him.[5] Mullen played only 47 games in 1990–91, scoring 17 goals and 39 points. He missed the last two months of the regular season after having surgery to remove a herniated disc in his back,[26] an injury for which he could not identify a specific check or incident as the cause.[27] He returned for the third game of the Penguins' first-round playoff series against the New Jersey Devils, scoring a goal. Mullen finished the 1991 Stanley Cup Playoffs with eight goals, including two in game six of the final, an 8–0 victory over the Minnesota North Stars that clinched Pittsburgh's first Stanley Cup.[26]

Healthy throughout the 1991–92 season, Mullen rebounded offensively to score 42 goals and 87 points in 77 games.[4] Midway through the season, he became the first player in Penguins' history to have consecutive four-goal games, doing so against the New York Islanders on December 23, 1991, and the Toronto Maple Leafs three days later.[28] He appeared in only nine playoff games, however, as he suffered a knee injury that required surgery to repair in the second game of Pittsburgh's second-round series against the New York Rangers.[29] Mullen watched from the sidelines as the Penguins repeated as Stanley Cup champions.[5]

Mullen tested free agency prior to the 1992–93 season, but ultimately chose to remain with the Penguins.[29] He missed the first month of the season while recovering from his knee surgery,[29] but finished the season with 33 goals and 70 points in 72 games. He added 6 points in 12 playoff games,[4] but the Penguins' attempt at a third consecutive championship ended with a second-round loss to the New York Islanders.[30] A 38-goal season in 1993–94 led to Mullen's third All-Star Game appearance. The game was a homecoming of sorts for Mullen, as it was played in Madison Square Garden.[31]

Mullen made his first appearance with the United States National Team following his graduation from Boston College.[16] He appeared in eight games at the 1979 World Ice Hockey Championships, scoring seven goals and adding an assist for the seventh place Americans.[39] He was a member of three Canada Cup teams, appearing at the 1984, 1987 and 1991 tournaments.[4] He scored two goals in the 1991 tournament, both of which came in a 7–3 semi-final victory over Finland that led the United States into their first tournament final.[40] The Americans settled for second place, however, after losing to Canada in the championship series.[39]

At the age of 41, Mullen emerged from retirement to join the Americans for a qualifying tournament leading into the 1999 Men's World Ice Hockey Championships.[41] The United States had a disastrous 12th-place finish in the 1998 tournament, requiring them to go into a qualifying round to avoid relegation to the B division for 1999.[42] As the qualifying tournament was played in November, American NHL players were not available.[41] Mullen recorded three assists in three games,[4] and helped the Americans stay in the top division for the 1999 tournament.[43]

"Mully spent a career excelling in areas of the ice a lot of guys wouldn't visit on a threat of death. Great balance on his skates. Great desire. Great teammate. A little guy with big talent and a huge heart."

Mullen arrived in the NHL possessing great balance on his skates, an ability his teammates and coaches believed he gained from playing roller hockey.[3] His coaches praised his willingness to play in the difficult areas of the ice, even though he stood only five foot nine inches tall and knew he would have to take a hit to make a play.[20] Penguins' play-by-play announcer Mike Lange nicknamed Mullen "Slippery Rock Joe" for his ability to evade opposing players.[44]

Mullen and his wife, Linda, have four children: sons Ryan, Michael and Patrick, and a daughter: Erin.[58] Patrick is also a professional hockey player. He signed a contract with the Ottawa Senators organization for the 2013–14 season.